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/* This file is part of the OpenLB library
*
* Copyright (C) 2017 Albert Mink, Marc Haussmann
* E-mail contact: info@openlb.net
* The most recent release of OpenLB can be downloaded at
* <http://www.openlb.net/>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/** \file
* Function to extract refractive properties needed for boundary modeling.
*/
#include "core/radiativeUnitConverter.h"
// definition required only by cygwin
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
/// All OpenLB code is contained in this namespace.
namespace olb {
/// Documentation of implemented functions found in 5.2.2 Biomedical Optics, Principles and Imaging; Wang 2007
double getThetaRefracted(double const& thetaIncident, double const& refractiveRelative)
{
double thetaRefracted = M_PI/2.;
if( refractiveRelative * sin(thetaIncident) < 1 ) {
thetaRefracted = asin( refractiveRelative * sin(thetaIncident)); // eq.(5.118)
}
return thetaRefracted;
};
double getFresnelFunction(double const& theta, double const& refractiveRelative)
{
double thetaRefracted = getThetaRefracted(theta, refractiveRelative);
double rf_1 = 0.5 * pow((refractiveRelative * cos(thetaRefracted) - cos(theta)) /
(refractiveRelative * cos(thetaRefracted) + cos(theta)), 2.);
double rf_2 = 0.5 * pow((refractiveRelative * cos(theta) - cos(thetaRefracted)) /
(refractiveRelative * cos(theta) + cos(thetaRefracted)), 2.);
return rf_1 + rf_2; // eq.(5.115)
};
double R_phi_diff (double const& theta, double const& refractiveRelative)
{
return 2. * sin(theta) * cos(theta) * getFresnelFunction(theta,refractiveRelative);
};
double R_j_diff (double const& theta, double const& refractiveRelative)
{
return 3. * sin(theta) * pow(cos(theta),2.) * getFresnelFunction(theta,refractiveRelative);
};
double getRefractionFunction(const double& refractiveRelative)
{
int N = 10000.0;
double h = (M_PI / 2.) /double(N);
double R_phi = 0.0;
double R_j = 0.0;
for (int i = 0; i < N; i++) {
R_phi += h*(R_phi_diff(0.5*h + h*i,refractiveRelative));
R_j += h*(R_j_diff (0.5*h + h*i,refractiveRelative));
}
double R_eff = (R_phi + R_j) / (2 - R_phi + R_j); // eq.(5.112)
return (1 + R_eff) / (1 - R_eff); // eq.(5.111) C_R = (1 + R_eff) / (1 - R_eff);
};
double getPartialBBCoefficient(double const& latticeDiffusionCoefficient, double const& relativeRefractiveIndex )
{
double C_R = getRefractionFunction( relativeRefractiveIndex );
return 2 - 2/(4*latticeDiffusionCoefficient*C_R +1);
};
} // namespace olb
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